title: Structural basis for Ca2+ -dependent formation of ALG-2/Alix peptide complex: Ca2+/EF3-driven arginine switch mechanism.
abstract: ALG-2 belongs to the penta-EF-hand (PEF) protein family and interacts with various intracellular proteins, such as Alix and TSG101, that are involved in endosomal sorting and HIV budding. Through X-ray crystallography, we solved the structures of Ca(2+)-free and -bound forms of N-terminally truncated human ALG-2 (des3-20ALG-2), Zn(2+)-bound form of full-length ALG-2, and the structure of the complex between des3-23ALG-2 and the peptide corresponding to Alix799-814 in Zn(2+)-bound form. Binding of Ca(2+) to EF3 enables the side chain of Arg125, present in the loop connecting EF3 and EF4, to move enough to make a primary hydrophobic pocket accessible to the critical PPYP motif, which partially overlaps with the GPP motif for the binding of Cep55 (centrosome protein 55 kDa). Based on these results, together with the results of in vitro binding assay with mutant ALG-2 and Alix proteins, we propose a Ca(2+)/EF3-driven arginine switch mechanism for ALG-2 binding to Alix.
authors.affiliation: Department of Applied Molecular Biosciences, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan.
authors.forename: Hironori
authors.initials: H
authors.lastname: Suzuki
authors.forename: Masato
authors.initials: M
authors.lastname: Kawasaki
authors.forename: Tatsutoshi
authors.initials: T
authors.lastname: Inuzuka
authors.forename: Mayumi
authors.initials: M
authors.lastname: Okumura
authors.forename: Takeshi
authors.initials: T
authors.lastname: Kakiuchi
authors.forename: Hideki
authors.initials: H
authors.lastname: Shibata
authors.forename: Soichi
authors.initials: S
authors.lastname: Wakatsuki
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Maki
mesh_terms: D000595:Amino Acid Sequence; D051017:Apoptosis Regulatory Proteins / Q000737:chemistry* / Q000378:metabolism*; D001120:Arginine / Q000737:chemistry / Q000378:metabolism*; D001665:Binding Sites; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology*; D002135:Calcium-Binding Proteins / Q000737:chemistry* / Q000378:metabolism*; D018797:Cell Cycle Proteins / Q000737:chemistry / Q000378:metabolism*; D018360:Crystallography, X-Ray; D020832:EF Hand Motifs / Q000502:physiology*; D056827:Endosomal Sorting Complexes Required for Transport; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism; D011485:Protein Binding / Q000187:drug effects; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid
chemical_list: D051017:Apoptosis Regulatory Proteins; D002135:Calcium-Binding Proteins; D018797:Cell Cycle Proteins; D056827:Endosomal Sorting Complexes Required for Transport; C097753:PDCD6 protein, human; C117020:PDCD6IP protein, human; D010446:Peptide Fragments; D001120:Arginine; D002118:Calcium